Mixing device



R. L. BATES MIXING DEVICE July 27, 71965 2 Sheets-Sheet 1 Filed Oct. 11, 1963 INVENTOR.

ROBERT L. BATES WMM@ ATTORNEYS July 27, 1965 AT 3,197,180

MIXING DEVICE Filed 001',- ll, 1963 2 Sheets-Sheet 2 INVENTOR.

Y ROBERT L. BATES ATTORNEYS United States Patent 3,197,180 1 MTXENG DEVICE Robert L. Bates, Dayton, Ghio, assignor to Chemineer, Inc., Dayton, flhio, a corporation of Ohio Filed Oct. 11, 1963, Ser. No. 315,528 4 Claims. (Cl. 259-7) This invention relates to a mixing device and more particularly to an improved paste or paddle mixer and the like.

Paddle mixers to which the present invention relates are laminar or viscous flow devices generally utilized with liquid, or liquid solid dispersions wherein the material has a substantially high viscosity, generally in the order of 5,000 to 500,000 centipoises. The materials usually mixed in paste or paddle mixers include high viscosity materials, relatively non-flowable or non-Newtonian materials, that is, materials which do not have a constant viscosity for varying shear rates, and typical such materials would be sealants, caulking compounds, paint and ink compositions, adhesives, mastics, and the like.

The paste or paddle mixers heretofore used were of two general types, the vertical paste mixer and the horizontal paste mixer, the devices being so contructed and arranged that the mixing paddles, drive shaft and container are arranged in the vertical and horizontal planes, respectively. In each of these type paste mixers, a stationary bafile is mounted in the container with the drive shaft centered therein and carrying a plurality of bafiles driven by the shaft and adapted to movement in a noninterfering manner between the stationary bafiles. The mixing is accomplished by the relative movement between the stationary and fixed bafl les as well as the relative movement between the movable bafiies and the wall, thereby providing a shearing action which brings about blending and wetting.

In the case of the vertically arranged paddle mixer, the plurality of spaced stationary baffles are generally rigidly mounted all at one end and extend downwardly into the container. Mounted over the container is a drive unti including a shaft whichextends downwardly into the container. The shaft carries a plurality of upwardly extending movable and driven baflies adapted to be rotated in non-interfering movement between the stationary baflies. With this particular construction there is adequate end to end mixing, but top to bottom mixing or turnover is somewhat less than desired. There are also practical limitations on the size of the unit due to the difficulty of fabricating stationary and movable baffles of sufficient length, strength and rigidity to provide eflicient mixing, particularly in the case of materials having a relatively low viscosity within the range of viscosity with which this type equipment is used. As the size of the container increases, it is usually necessary to increase the length of the paddles and ultimately a point is reached which limits the size of the mixer because the paddles must be increased, requiring additional horsepower to drive the movable paddles, and the resultant structure economically inefiicient. The usual procedure is to use two such devices capable of handling for example 250 gallons of material each in order to make most efiicient use of input power. Furthermore, the vertically arranged paste mixer generally is emptied by a discharge outlet located at the lower end of the vertically extending container wall, and it is difficult to empty the container completely because of the viscosity of the materials being utilized. For example in a unit capable of handling 250 gallons, the last five or six inches of material are removed only with some difiiculty.

In the vertically arranged paddle mixer, the motor and "ice drive unit is generally mounted vertically above the container'with the shaft extending vertically downwardly. This mechanical arrangement, which is convenient and relatively simple, renders it somewhat difiicult to provide a sealed mixing container particularly in instances wherein volatile or dangerous solvents constitute a component of the mixture or where it is desirable to have a vacuum or exclude air from the container. Another shortcom ing of this particular type unit is the fact that powder tends to adhere to that portion of the shaft disposed in the mixing drum, and also to some extent dry materials tend to collect along the inner peripheral wall of the drum. To eliminate this, a stationary baflle is generally positioned in wiping relationship with the shaft, while movable baflle closest to the inside periphery of the container carries a wiper arm to remove material which tends to collect along the surface of the drum.

Another characteristic of this type unit is the relatively large free surface area of material being mixed with respect to the total volume of the container thereby creating a condition which allows air to be folded in and which is somewhat diflicult to remove from viscous materials.

In the case of the horizontal paste mixer, the baffles, shaft container are mounted on a horizontal plane, and during the mixing operation, which is essentially blending and wetting of viscous materials in a homogeneous mass, there may result Stratification or zone mixing, which in the case of the horizontally arranged paste mixer amounts to top to bottom mixing with stratification occurring in zones disposed or arranged along the horizontal axis of the mixer. This particular construction does not provide efiicient end to end mixing which is desirable in order to provide products having substantially uniform characteristics throughout the entire batch during mixing. While Stratification may be reduced in this type mixer by proper procedures for adding the materials to be mixed, the mixer itself, absent such precautions, tends inherently to cause such stratification.

Accordingly, it is a primary object of the present invention to provide an improved paddle or paste mixer having overall improved characteristics, particularly top to bottom mixing and end to end intermixing, especially with materials of relatively high viscosity.

Another object of the present invention is to provide an improved laminar flow mixing device for materials having a viscosity in the range of 5,000 to 500,000 centipoises, and which is disposed at an angle between the horizontal and vertical thereby providing eflicient mixing in all planes and allowing easy draining and substantially eliminating collection and adherence of materials to be mixed on the drive shaft or bafiles thereof.

A further object of the present invention is to provide a laminar flow mixing device which is disposed at an angle between the horizontal and vertical thereby providing efficient top to bottom mixing as well as end to end intermixing, and wherein the drive unit therefor is so mounted as to allow the mixing drum to be conveniently and simply sealed in the event that toxic or explosive solvents are utilized, or in the event that it is necessary to exclude air or maintain vacuum conditions within the mixing drum.

A further object of the present invention is to provide an improved paddle or paste mixer wherein the mixing drum is inclined with respect to the horizontal plane, and wherein the ratio of free surface area to total batch volume of material being mixed is relatively low thereby substantially reducing the tendency to entrap air in the material being mixed.

A further object of the present invention is to provide an improved paddle or paste mixer for use in noneNewtonian materials wherein the mixing drum is disposed at an angle between and 40 relative to the horizontal plane thereby providing top to bottom mixing and end to end intermixing, while substantially eliminating collection or adherence of the materials to be mixed on the drive shaft or baffles.

Other objects and advantages of the invention will be apparent from the following description, the accompanying drawings and the appended claims.

In the drawings:

FIG. 1 is a view in perspective of the paddle mixer in accordance with the present invention;

FIG. 2 is a view partly in section and partly in elevation showing the interior arrangement of the paddle mixer in accordance with the present invention;

FIG. 3 is an end view from the right of FIG. 1 of the paddle mixer of the present invention; and

FIG. 4 is a view in perspective of the drive shaft and movable baffles for use in a paddle mixer of the present invention.

Referring to the drawings, which illustrate a preferred embodiment of the present invention, the paste mixer it) shown in FIGS. 1 and 2 includes a fluid tight hollow cylindrical body or container 12 having a bottom end face 14 and'a top face 15. The hollow cylindrical body 12 is supported at an angle between about 20 to 40 from the horizontal 'by I a supporting structure which includes a pair of vertically extending legs 16 mounted on the body, and a plurality of legs 18 mounted on the body and disposed at an angle with respect to the vertical plane. Joining each pair of legs 16 and 18 is a cross brace 19 which provides a rigid supporting structure for the paste mixer. Mounted on the top end face 15 is a supporting structure .20 which operates as a housing for a seal assembly and as a supporting structure for a drive mechanism 25. The lower end face 14 has aihxed thereto a supporting member 26 for the bearing assembly 28.

Each end of the body 12 is provided with an aperture through which passes a drive shaft 30 supported at the lower end by bearing 28 and at the upper end by a bearing, not shown. The lower end of the shaft 34 is sealed to the lower end face 14 by a suitable seal 32 which may be in the form of a lip seal, a mechanical seal, or a stufiing box seal as illustrated schematically in the drawing, while the upper end of the shaft 39 is sealed to the top end face 15 by a second seal 33 similar in construction to seal assembly 32.

' Afiixed to 'the supporting structure 20 is a driven gear unit 35 which is operatively connected to a motor 36 through an endless belt assembly 37, the gear unit and motor being supported on brackets 38 afiixed to the supporting structure 20. One advantage'of the inclined paste mixer of the present invention is the lateral displacement or location of the motor and drive unit with respect to the container or mixer body, thereby providing easy access and simplifying the construction of the drive assembly.

As shown in FIGS. 1 and 3, the body 12 is provided with a cover 40 hinged at 42 to swing completely out of the way of the container to expose the interior thereof. The cover 40 is held in sealing relationship to the body by a plurality of wing bolts 43 which force a cooperating clamp element 44 into engagement with the container body and cover. The cover also includes a hopper unit 45 through which the materials to be mixed may be added to the container and the hopper 45 is preferably located adjacent the top end face 15, and diagonally disposed with respect to a discharge aperture 46 located in the lower end face 14 and disposed vertically below and laterally spaced from the hopper 45. The discharge member includes a plate 48 slidable in a pair of grooves (not shown), and operated by assembly 49.

Positioned within the container are stationary bafiies 50 and movable bafiies 51 and 53, the stationary baffles 59 being disposed in parallel spaced relationship and mounted on a stationary bafile arm 54 which extends through the cylindrical wall section of the body to position the stationary bafile arms evenly from between end faces 14 and 15. The movable baflies 51 and 53 shown in FEGS. 2 and 4 include baffle arms 55 and 57 disposed within the container in parallel spaced relationship with the end faces 14 and 15 and mounted on the shaft 353 for rotation therewith. The movable bafiie arms 56 and 57 are preferably arranged on the shaft 39 in a displaced relationship so that the axis of the baffle arm 56 is preferably perpendicular to the axis of battle arm 57. The bafile arms 51 and 53 are arranged on the respective baflie arms in parallel spaced relationship and are sufiiciently long for interfitting rotational and noninterfering movementthrough the stationary baffle arms 58'. As shown in FIG. 2, movable baflies which are fartl est away from the shaft are preferably somewhat longer than the remainder, although all of the arms may be of equal length if desired.

in operation, the discharge aperture 46 is closed, the wing bolts 4-3 are tightened to provide a seal between the cover 4% and the body 12, and the liquid or relatively viscous material to be mixed is introduced into the container through hopper 45. Thereafter other materials may be added through the hopper 45 as may be required during operation of the inclined paste mixer of the present invention. Because of the annular displacement of between 20 and 40 with respect to the horizontal plane, and the inclined axis of the movable baffles, the paste mixer of the present invention provides improved top to bottom mixing as well as end to end intermixing during operation thereof.

The flow pattern is counterclockwise as viewed in FIG. 2, due to the fact that effect of gravitational forces and the movement of the movable battles operate in different planes. Gravity tends to cause the material in the container to how downward towards the discharge aperture while the movable baflies tend to move the material from the discharge aperture towards the hopper, and there is no stratification or stagnation of the material in the container during a mixing operation.

As shown in FIG. 2, there is preferably present in the container 21 sufiicient amount of material to cover that portion of the drive shaft 39 which is within the mixer thereby preventing accumulation of solid materials on the shaft during a mixing operation. .Additionally, the inclined arrangement of the container operates to provide a relatively low ratio of free surface area of liquid to total batch volume thereby substantially reducing or eliminating blending in of air with the material being mixed.

Solids are frequently added to the material being mixed with the paddle or paste mixer of the type to which this invention relates, and as will be seen from FIG. 2, the movable baffles pass the hopper thereby wetting these solid materials into the mixture. Further, the fact that the shaft 3% is covered with material Within the container prevents powder from adhering thereto, and no solid material adheres either to baffles 51 or 53 since they are moving through the material being mixed and they pass between stationary bafiies 50. Shear is created as a result of the rotation of the movable bafiies and the tendency of the relatively viscous material to resist agitation and the additional shear as the movable bafiies sequentially pass the stationary bafiies.

The paste mixer of the present invention also offers the advantage of easy drainage since the discharge aperture 46 is located at the lowermost portion of the bottom end face 14, and the full head of the material assists in forcing it out of the container once the mixing operation has been completed. Additionally, clean up is rendered simple by the pivotal arrangement of the hinged cover which may be moved exposing a substantial portion of the interior of the container since the drive mechanism may be mounted on an end face.

Additionally, the

33 inclined feature allows construction of paste mixers having increased capacity by increasing either the diameter of the cylindrical section or its length while also providing top to bottom intermixing, a feature not found in vertically disposed paste mixers, and end to end mixing, a feature not found in horizontally disposed mixers.

While the forms of apparatus herein described constitute a preferred embodiment of the invention, it is to be understood that the invention is not limited to this precise [form of apparatus, and that changes may be made therein without departing from the scope or" the invention which is defined in the appended claims.

What is claimed is:

1. A paste mixer of the type described comprising means defining a fluid tight generally cylindrical container, a plurality of spaced stationary baffles mounted in said container in parallel relation to the cylindrical wall thereof, a plurality of movable bafiies mounted in parallel relation to the cylindrical wall of said container for non-interfering movement between said stationary baflies, means cooperating with said container and driving said movable baflies, said container including means defining a hopper for introduction of material to be mixed into said container, discharge means in said container disposed generally diagonally with respect to said hopper means for removal of the material being mixed within said container, means supporting said container at an angle of between about 20 to 40 from the horizontal, and said stationary bafiies cooperating with said movable bafiies to produce shear with respect to the material being mixed.

2. A paste mixer for materials having a viscosity in the range of 5,000 to 500,000 oentipoises comprising means defining a fluid tight hollow cylindrical body having a pair of spaced end faces, a plurality of spaced stationary baffles mounted in said body in parallel relation thereto, a plurality of movable bafiles mounted in parallel relation to said body for non-interfering movement between said stationary baffles, drive shaft means extending in sealed relation through said end faces and carrying said movable bafiies, means supported by one of said end faces and connected in driving relation to said shaft means, said body including a hinged cover having means defining a hopper for introduction of material to be mixed into said body, discharge means in one of said end faces opposite said drive means disposed generally diagonally with respect to said hopper means for removal of the material being mixed within said body, means supporting said body at an angle of between about 20 to 40 from the horizontal with said hopper means disposed vertically above and laterally spaced from said discharge means, and said movable and stationary bafiies cooperating with said angulanly disposed body to effect top to bottom mixing and end to end intermixing.

3. A paste mixer for materials having a viscosity in the range of 5,000 to 500,000 centipoises comprising means defining a fluid tight hollow cylindrical body having top and bottom spaced end faces, a plurality of spaced stationary baffies mounted in said body in parallel relation thereto and spaced from said end faces, a pair of spaced movable bafiie arms mounted in said body and in parallel spaced relation with said end faces, each said baflie arm carrying a plurality of spaced baflies of sufficient length for interfitting and non-interfering movement with respect to said stationary baflies, drive shaft means extending in sealed relation through said end faces and carrying said baflie arms for rotation therewith, means supported by said top end face and connected in driving relation to said shaft means, said body including means defining a hopper for introduction of material to be mixed into said body, discharge means in said bottom end face disposed generally diagonally with respect to said hopper means for removal of the material being mixed within said body, and means supporting said body at an angle of between about 20 to 40 from the horizontal with said hopper means disposed vertically above and laterally spaced from said discharge means, and said movable and stationary bafiles cooperating with said angularly disposed body to effect top to bottom mixing and end to end intermixing while maintaining said drive shaft means wetted with material being mixed and free of powdered materials introduced into said body.

4. A paste mixer for materials having a viscosity in the range of 5,000 to 500,000 centipoises comprising means defining a fluid tight hollow cylindrical body havin top and bottom spaced parallel end faces, means mounting a plurality of spaced stationary baffles in said body in parallel relation thereto and spaced from said end faces, a pair of spaced movable bafile arms mounted in said body and in parallel spaced relation with said end faces, each said baffle arm carrying a plurality of spaced battles of sufficient length for interfitting and non-interfering movement with respect to said stationary baffles, drive shaft means extending in sealed relation through said end faces, said bafile arms being mounted on said drive shaft and displaced from each other, means supported by said top end face and connected in driving relation to said shaft means, said body including a hinged cover having means defining a hopper for introduction of material to be mixed into said body, discharge means in said bottom end face and disposed generally diagonally with respect to said hopper means for removal of the material being mixed Within said body, means supporting said body at an angle of between about 20 to 40 from the horizontal with said hopper means disposed vertically above and later-ally spaced from said discharge means, and said movable and stationary baflies cooperating with said angularly disposed body to effect top to bottom mixing and end to end inter-mixing while maintaining said drive shaft means wetted with material being mixed and free of powdered materials introduced into said body.

References Cited by the Examiner UNITED STATES PATENTS 2,608,395 8/52 August 259-461 CHARLES A. WILLMUTH, Primary Examiner. 

1. A PASTE MIXER OF THE TYPE DESCRIBED COMPRISING MEANS DEFINING A FLUID TIGHT GENERALLY CYLINDRICAL CONTAINER, A PLURALTIY OF SPACED STATIONARY BAFFIES MOUNTED IN SAID CONTAINER IN PARALLEL RELATTION TO THE CYLINDRICAL WALL THEREOF, A PLURALITY OF MOVABLE BAFFLES MOUNTED IN PARALLEL RELATTION TO THE CYLINDRICAL WALL OF SAID CONTAINER FOR NON-INTERFERING MOVEMENT BETWEEN SAID STATIONARY BAFFLES, MEANS COOPERATING WITH SAID CONTAINER AND DRIVING SAID MOVABLE BAFFLES, SAID CONTAINER INCLUDING MEANS DEFINING A HOPPER FOR INTRODUCTION OF MATERIAL TO BE MIXED INTO SAID CONTAINER, DISCHARGE MEANS IN SAID CONTAINER DISPOSED GENERALLY DIAGONALLY WITH RESPECT TO SAID HOPPER MEANS FOR REMOVAL OF THE MATERIAL BEING MIXED WITHIN SAID CONTAINER, MEANS SUPPORTING SAID CONTAINER AT AN ANGLE OF BETWEEN ABOUT 20* TO 40* FROM THE HORIZONTAL AND SAID STATIONARY BAFFLES COOPERATING WITH SAID MOVABLE BAFFLES TO PRODUCE SHEAR WITH RESPECT TO THE MATERIAL BEING MIXED. 